A test for comparing the means of two samples, or the mean of one sample (or even parameter estimates) with a specified value; also known as the "Student t-test" after the pseudonym of its inventor.

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19 views

Test for significance of variation in time series data

Suppose a DMV office runs driving tests. Every week a number of people take the driving test, some pass and some fail. Looking at this data set, we notice that the pass rate varies from week to week. ...
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17 views

Is it possible to compare 2 groups while controlling for something?

Is it possible to compare two groups (e.g., t-test, Wilcoxon, Mann-Whitney test, etc.) while controlling for something? E.g., I want to compare home ownership between military veterans and non-...
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13 views

A/B Testing - Risk of excluding guests

I have a sample of 1.6 million users who were split 80/20. 80% of the guests were treated with a message and 20% were shown nothing. ~5% of the guests converted in BOTH populations... but the ...
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1answer
20 views

Advance Methods of Understanding Significance of Customer Behaviors

I currently own a couple of websites and lately I've been implementing some feature changes - I've noticed some changes in website traffic and I was wondering what some of the more sophisticated ways ...
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2answers
121 views

Not able to understand the intuition behind $z$-test, $t$-test

I am not able to understand and appreciate the basic intuition behind need of this whole hypothesis testing framework, different kinds of tests, looking up tables, significance level etc etc. Why can'...
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2answers
10 views

Z-Test and T-test in SPSS custom table - Include 'Total' in comparision

I would like to not only compare columns' proportions and/or means but also each column's proportion and mean against the whole sample (i.e., the 'Total' column). Any way we can obtain that with SPSS ...
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1answer
21 views

when dependent variable is categorical with only 2 levels: t-test or chi-square goodness of fit?

Let's say I'm trying to compare if two groups of people are significantly different from each other in terms of their access to the internet. One could code each person's internet access ...
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13 views

multiple paired-sample t-test and Bonferroni Adjustment

I have 4 questionnaires: A,B,C,D. I also have another 4 items ($i_1,i_2.i_3,i_4$) that each measures some aspect of acceptability or feasibility of the questionnaires, which were answered following ...
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40 views

What statistical test can I use?

I'm currently trying to test the effect of pH on the growth of three different types of grasses for my dissertation and didn't account for number of replicates being used (statistically dumb). Here is ...
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7 views

significance between comparisions

I hope this is the right forum for this kind of question (otherwise please point me to the right one). We are working on a RNA-Seq data set (10 biological replica for three conditions). We have ...
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8 views

How to do contrasts in a significant interaction of 2 variables in a 4 four variable set?

I did an analysis of a 2x2x2x2 mixed factorial anova. The first 3 variables were repeated measures and the last was a between groups analysis. The data in the repeated measures were all reaction ...
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2answers
40 views

Can I use a paired t-test on data that are averages?

I am comparing 15 pairs of averages paired by two categories with a paired t test. The samples used to determine the averages in each pair are not equal within any single pair of data. For example, if ...
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21 views

Is an independent t-test the right choice for this question?

I was trying to figure out which test I need for analyzing my data. However, I guess by reading that much I confused myself. I analyzed two different retailers with respect to the availability of ...
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14 views

Should I use t-test or ANOVA+post hoc (two different treatments and a control)

I have been working with ice algaes,and Im looking on their fattyacids. Here is a bit about the experimental design. I have one treatment area, cleared, where I have removed all snow. I have ...
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15 views

Simulating probability through random sampling: Is this valid?

What is the name of a simulation that randomly takes two samples from a population and then compares it to another random sample with a predefined condition? I'm writing an assignment and I need some ...
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0answers
5 views

Comparing response options ordinal variable single sample

Is there a way to test if the difference between response options of an ordinal variable is statistically significant in a single sample? In my example, we asked 240 survey respondents how well an ...
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22 views

Multiple t tests with Bonferroni correction instead of Anova and posthoc?

I have a set of 6 experiments that were all performed at the same time. This consists of 3 genotypes (A, B, C) , each under two conditions (1 and 2) with a single measurement variable. I just want ...
3
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1answer
56 views

code Welch's t-test in C++ using approximations for student's t values

I need to code a Welch's t-test between two populations in C++ without using external libraries like, for example, boost. I know that given my two populations of size $N_1$ and $N_2$, I can calculate ...
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0answers
20 views

Which statistical test should I use to assess the impact of a trial between subjects over time?

In the following table, I'd like to determine if yield is significantly impacted by pesticide application (applied in seasons 7-10) or if the difference between the control field (A) and trial field (...
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20 views

Statistical tests to data organized by weekdays

I have data where there are numeric values (can be 0 also) for corresponding weekdays (1=monday, 2=tuesday, 7=sunday etc). I want to find out if my values (say, for temperature for example) depends on ...
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0answers
9 views

Multiple t-tests and interpreting the winner

If you have a question with 3 answer choices and you order them in order of most picked to least pick and run t tests and the top is not sig dif from the middle and the middle is not sig dif from the ...
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0answers
10 views

How are independent t-tests affected by unequal Ns?

For example, if I have 11 participants giving one type of response, and 6 participants giving a different type of response. I want to compare the response latency between these two 'groups' of ...
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10 views

What statistical test to use..RM Anova?

I am looking at the effect of darkness on plant stress. I have two treatments (light and dark) with 3 replicates in each treatment. Samples were taken at time points 0 days through to 100 days (0,3,7,...
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1answer
59 views

Paired t-test to test trends in regression coefficients between groups

I have data where I estimate regression coefficients/slopes for two groups (e.g. sex-specific regression coefficients) for a number of single effect regression models. I have used Bayesian methods ...
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2answers
37 views

Is ANCOVA correct here?

I am analyzing data from a mindfulness intervention in which 60 participants took part in an ipod-based intervention listening to meditation tracks. Outcome measures on anxiety, depression, stress, ...
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2answers
89 views

Aggregation of Correlations Coefficients (Spearman)

in an analysis of survey data, I have to deal with multilevel/three-dimensional data. Now, I need to aggregate correlation coefficients found on the individual level (between individual rank-orders) ...
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1answer
23 views

Multilevel alternative to Paired t-test

I have a problem where we have N patients, and we measure some property of tumoral lesions for each patient, where the number of lesions varies on each patient (patient A could have 1 lesion, and ...
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24 views

How to compare experimental results of multiple models using significance tests?

I am using 5-fold cross validation to evaluate the errors of 10 models. Therefore, there are 50 results (each model has 5 error values generated from 5 random evaluation partitions). My question is: ...
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12 views

Nested model instead of 5 individual t-tests?

I am trying to compare a test with three replicates to a reference with 9 replicates. My setup is the following: 2 completely different test methods (A, B). Each Method is seperated into 3 ...
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1answer
22 views

Derive z- or t-statistic from p-values of regression coefficients from a probit/logit model

I have the results from an empirical study reporting the results for a probit and logit model. They just report the p-values of the regression coefficients. I want to derive the corresponding $t$-/$z$-...
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1answer
20 views

Determining two most similar objects based on multiple variables

I am trying to determine the two most similar years based on a number of environmentally variables. For example, I would like to choose the most similar year to 2015, from the set 1989 to 2016, based ...
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1answer
40 views

Can I run statistical tests on descriptive statistics like mean and standard deviation? (i.e. no raw data)

I'm trying to figure out which statistical test to run on my data, but it has been processed so that now I have gathered the mean and standard deviation values to be used instead of the raw data. I ...
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10 views

Poisson Regression vs. T-test for Balance

I have many subjects that were cluster-randomized to a treatment group and to a control group. I want to check the age balance of the groups following the randomization - e.g. whether there is a ...
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45 views

Why does a p-value of 2.4 indicate a very small probability that rejecting H0 is incorrect?

I am working with body temperatures in R, conducting a t-test. It is widely believed that the average body temperature for healthy adults is 98.6 degrees Fahrenheit. The body temperatures of $n = ...
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1answer
42 views

Why would one ever use z-score over a t-score?

Forgive me if this seems like an elementary question, but no amount of googling has turned up a satisfying answer for me. From what I understand, a t-score should be used instead of a z-score when the ...
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16 views

What's the difference between t-test and sequential F-test?

I just started learning linear regression, and I couldn't completely understand the difference. I know the t-test is testing NH:$\beta_i = 0$ and AH: $\beta_i \neq 0$. The overall F-test is testing ...
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2answers
35 views

Can you derive Standard Deviations from a raw mean difference and p-value?

I have mean averages and a p-value, which I assume was of a t -test. This is the information provided to me: Treatment N =121 Control N=107 treatment mean = 356.700 treatment control= 357.560 ...
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1answer
42 views

Can I interpret mean difference on a Likert scale as a percentage change

I have pre-test data showing a mean of 3.71 for work-stress (7 point likert scale). My post-test data shows a mean of 3.24 for work-stress (same 7 point likert scale). Paired sample t-test is ...
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1answer
37 views

Paired t-test with small standard error

I am comparing two algorithms applied to all frames of a video clip. To evaluate the result I am doing a paired t-test analysis, i.e., I am subtracting the algorithm scores for each frame and then ...
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0answers
15 views

Identify differentially expressed genes across genotypes

I have 40 different genotypes of rice. For each genotype, I have two replicates under control treatment and two replicates under drought treatment. We sequenced those samples and get read counts of ...
2
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2answers
52 views

How do I avoid multiple t-tests (or is it ok to use multiple t tests here?)

I've searched around CV for a bit, and have not found a good answer as to what test to use instead of multiple t-tests in my particular situation. I am interested in comparing mean size (of fish) ...
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1answer
38 views

How to test multiple comparisons of means of variables in R

I have a multiple N (>20) variables. I want to test $H_0$ that in at least one pair of them one variable have significantly higher values then the other. I know that I can perform a bunch of $\frac{...
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0answers
14 views

statistical test to compare numerical data pre and post intervention

For my research I will be comparing the mean number of screening tests performed before implementation of an intervention and after. The pre and post groups are not the exact same participants. The ...
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3answers
143 views

Real-world example on significance testing with large samples

The issues that arise when one uses statistical hypothesis testing framework with large samples are dissussed on CV (see e.g. this thread). The main problem discussed there is that in the real world ...
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0answers
7 views

How do I find if two categories of ratio data are different in a manner that is statistically significant?

I have 4 categories of data, A, B, C, and D, that are ratios (market share). Each category has different numbers of records (prescriber-level data). Each record is a market share percentage that is ...
1
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1answer
31 views

one sample t-tests applied to each row - 'data are essentially constant' error

I have three replicates of an experiment which gives me ratios of the abundance of different peptides. If I take the data for one peptide: ...
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0answers
28 views

What is it that you're doing when you do a single t test on one predictor of a multiple regression model?

I hope my interpretation is correct. When you're doing a t-test on a single predictor of a multiple regression model, are you looking at how it behaves while the other coefficients are fixed?
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23 views

Paired T-test vs. Survey Design T-Test with Stratification

What is the difference between survey design based approaches to t-tests when there is a stratified sample and paired t-tests where the pairs are the strata? For example, in R there is a svyttest() ...
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74 views

Single Sample t-test Hypothesis Confusion

In case you want data set.seed(100) hotel <- rep(1,100) hotel <- unlist(lapply(hotel, function(x) { runif(1,1,5) } )) NULL Hypothesis :- Hotel rating is ...
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1answer
32 views

Performing a t-test with discrete (currency) data

I want to perform a 2 sample t-test assuming unequal variances, however my variable is currency. Currency is discrete, however when checking the assumptions of the t-test, I see that the data should ...